Difference between revisions of "Sql Server 2012 - Three-Valued Logic"
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A predicate can evaluate | A predicate can evaluate | ||
to true, false, and unknown. This type of logic is known as three-valued logic<br> | to true, false, and unknown. This type of logic is known as three-valued logic<br> | ||
| + | when region is NULL, the predicate region <> <br> | ||
| + | 'WA' evaluates to unknown, and the row is discarded | ||
Revision as of 12:44, 25 April 2016
The type of logic used in such a
case is known as two-valued logic. The WHERE filter returns only the rows for which the predicate
evaluates to true
A predicate can evaluate
to true, false, and unknown. This type of logic is known as three-valued logic
when region is NULL, the predicate region <>
'WA' evaluates to unknown, and the row is discarded
